The present invention relates to a shading correction circuit and method in an image processing system that scans a document to binarize an image of the scanned document, and more particularly, to a shading correction circuit and method capable of removing adverse effects due to impulse noise, or dust which may be accumulated on a white panel or roller.
A conventional image scanning device photoelectrically reads an image on a document using an image sensor, such as a charge-coupled device CCD. In reading the image, the density of the read image may vary due to variations in a light source for illuminating a read object or in other optical members, or due to nonuniform sensitivity of a plurality of light-receiving elements of the image sensor. In view of this problem, a shading correction operation can be implemented to enable image reading to be performed with a high degree of reliability. Conventional means for performing shading correction are disclosed, for example, in U.S. Pat. No. 5,001,768 entitled Image Reading Apparatus and issued to Mita et al. which performs shading correction using a logarithmic conversion scheme. While this type of conventional scheme possesses merit in its own right, I believe that an improved circuit and method for performing shading correction that avoids reliance on logarithmic conversions can be contemplated.